The moment Microsoft announced it would lock other browsers out of being installed on Windows RT, we all knew regulatory bodies the world over were wringing their hands. Today, this has been confirmed: in the wake of an investigation into Microsoft not complying with the existing antitrust rulings regarding browser choice, the EU has also announced it's investigating Windows 8 x86 and Windows 8 RT (ARM).

For WindowsRT does not have a "long history of being a general purpose OS that can be installed on most hardware and customized to the user's tastes."

WindowsRT is like iOS in that:
WindowsRT apps can only come from the MS app store (exceptions made for people that develop their own apps.) And WindowsRT cannot be purchased by consumers. WindowsRT is only available as part of "integrated" hardware/software devices that are made for sale.

So, if your theories are indeed what allows Apple to get away with anything they want wrt iOS, then the EU doesn't hav a leg to stand on, since WindowsRT is the exact same thing. The EU would be complete and utter hypocrites if they attack Microsoft for WindowsRT while letting Apple do whatever the hell it wants wrt iOS.

P.S.
Note that WindowsRT can't run any Win32 apps, and therefore cannot take advantage of the apps that the "monopoly" OS runs. So x86 Windows being a "monopoly" OS is meaningless wrt WindowsRT. So the EU can't even use that argument with a straight face.

Maybe Microsoft should go even further and not allow sales of any WindowsRT devices in the EU except for their own Surface product. That would totally cement the "integrated hardware/software" argument in Microsoft's favor (though I think they already have that argument going for them, as I said in the parent post).

That would be the ultimate irony: If Microsoft responded to this EU action by choosing to make Surface the only WindowsRT product available in the EU, the EU couldn't do a damn thing about it and would have to shut down their "investigation" (since they couldn't get around the "integrated hardware/software solution" argument), and the EU would have nothing but themselves to blame for the reduction in consumer choices for EU citizens.

WindowsRT is like iOS in that:
WindowsRT apps can only come from the MS app store (exceptions made for people that develop their own apps.) And WindowsRT cannot be purchased by consumers. WindowsRT is only available as part of "integrated" hardware/software devices that are made for sale.

I think it has less to do with the "integrated" nature of the product than it does with monopoly power. The antitrust case in the early 2000s was specifically about x86-class computers. Microsoft doesn't have monopoly power in the ARM-based OS market. Technically speaking, nobody does, since the market is so broad and encompasses a wide swathe of mobile devices (phones, tablets, etc). My guess is that the EU is primarily interested in the x86 market, but is casting a wary eye at the ARM market to understand the competitive dynamics; either way, the EU really can't do much about ARM, given Microsoft's lack of monopoly power. Microsoft can pretty much do anything it wants there.

Antitrust matters aren't about killing monopolies in existing categories, it's about making sure those monopolies aren't used to extend it into new markets.

What Microsoft is doing with Windows 8 is text book antitrust behaviour: They use their x86 monopoly to push Metro, to reap the rewards (mindshare, applications) on ARM devices and in the mobile space.

The antitrust case in the early 2000s was specifically about x86-class computers. [...] My guess is that the EU is primarily interested in the x86 market, but is casting a wary eye at the ARM market to understand the competitive dynamics; either way, the EU really can't do much about ARM, given Microsoft's lack of monopoly power. Microsoft can pretty much do anything it wants there.

This might come as a shock to you, but the EU is not US ...and in the EU cases against MS, it wasn't really, as in the US, explicitly about ~Intel machines.

OTOH, the EU cases (and rulings, and big fines) were about so broad things as access to protocols, specifications to be used by 3rd party software vendors. The issue with browsers would probably fit those.